This invention relates to a flat metal sealing gasket, particularly a cylinder head gasket for an internal-combustion engine. The sealing gasket is of the type which is formed of a laminate composed of at least two superposed metal plates having peripheral recesses or thoroughgoing openings as well as projections extending from an inward edge of the recesses or thoroughgoing openings for a form-locking securement of the plates to one another.
For handling the installation-ready sealing gasket up to the installation work proper, a secure connection between the individual metal plates is necessary. Several techniques are known for connecting the individual sheet metal plates with one another in a non-releasable manner. Preferably additional components, such as rivets or framing rings have been used which are often mounted in additional thoroughgoing passages of the sealing gasket. Dependent on the geometry of the article and the number of the securing points the individual layers may not lie flat on one another. The terminal regions bent around the gasket edge may assist to remedy such undesired occurrence.
European Patent No. 500 273 discloses a flat sealing gasket of the above-outlined type in which at least two metal plates are connected with one another by securing means which is provided in the gasket regions where the sealing properties are not affected. Thus, in an opening of one of the plates a bendable strip is arranged which, after bending about 180.degree., lies on the edge of the opening of another plate. It is a disadvantage of such a structure that, similarly to arrangements where rivets are used, the bent-around tab or rivets lie on the outer plates and thus increase the thickness of the seal in those regions. To avoid such an occurrence, in three-layer assemblies the middle plate has been provided with a recess. While, in this manner, the sealing pressure on the gasket is not increased, the flanking plates nevertheless have to be additionally deformed which results in undesired stresses in the plates, increasing the risks of rupture and thus jeopardizing the sealing behavior.